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Reply To: | DesignerCouncil E-Mail Forum. |
Date: | Fri, 24 Sep 1999 09:41:26 -0700 |
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Jack,
First, let me correct your self perception: You are NOT "just a lowly layout
guy"! ;-) No need to be humble here. Stand up and take pride!!
Second, it is my understanding the IPC makes recommendations for pad sizes which
will accomodate most every vendors' process. So, perhaps the best thing to do
is start with that but then go to your assembly shop and ask their opinion of
whether the pad size(s) is/are suitable as is, or if it could be reduced to some
degree. I personally use the guidelines given by SMT Plus as it seems to be a
tweeked basis of the IPC standards and have had no trouble whatsoever.
Best regards,
Bill Gebhardt
Electrical Engineer/PCB Designer
Overland Data Inc.
San Diego, CA
Jack Olson <[log in to unmask]> on 09/24/99 09:16:48 AM
Please respond to "DesignerCouncil E-Mail Forum." <[log in to unmask]>;
Please respond to Jack Olson <[log in to unmask]>
To: [log in to unmask]
cc: (bcc: Bill Gebhardt/ENG/SanDiego/US)
Subject: Re: [DC] Pad Sizes for good solder Joints
That is a really good question, but I don't know how much response you will
get, because in my experience it is usually the opposite that happens. The
assembler wants to reduce the pad size and corresponding amount of solder
paste applied. I've never thought about how IPC says minimum, and how that
could be interpreted to mean that you should make everything bigger if you
can, because nobody does that! Everyone wants smaller smaller smaller
(except maybe big pads on through-hole for high-power components, or
something like that). So maybe you should take that "land sizes should be
maximized" statement with a grain of salt, since I believe the IPC
recommendations are already bigger than anyone else's out there. (correct me
if I'm wrong you guys, I'm just a lowly layout guy)
-----Original Message-----
From: Mark Holmes [mailto:[log in to unmask]]
Sent: Friday, September 24, 1999 1:09 AM
Subject: Pad Sizes for good solder Joints
All the data I have regarding pad sizes (e.g. IPC-2221
9.1.1) give examples
on how to calculate Minimum pad sizes, usually from a PCB
fabrication
standpoint. IPC-2221 states that all lands and annular ring
shall maximised
wherever feasible, consistent with good design requirements
and electrical
clearance requirements.
My questions are: How do I determine the pad size that will
give me the best
soldered joint?
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